package dk.itu.oop.lecture5;

import java.util.Iterator;

public class AlternateMerge extends MergeIterators{
	// inv: chooseFirst = true means that choose chose i2 last time, and i1 
	// will be chosen next time. chooseFirst = false means that choose chose
	// i1 last time, and will choose i2 next time.
	private boolean chooseFirst; 
	
	public AlternateMerge(OOPIterator itr1, OOPIterator itr2){
		super(itr1,itr2);
		chooseFirst = true;
	}
	
	/*pre: i1 and i2 both have elements left
	 *post: return either i1 or i2, but not the same twice in a row.
	 */
	protected OOPIterator choose(OOPIterator i1, OOPIterator i2){
		if (chooseFirst){
			chooseFirst = false;
			return i1;
		}else{
			chooseFirst = true;
			return i2;
		}
	}
}